Garage door operators have been conceived and constructed for over 40 years. The concept of a longitudinally stationary but rotating screw to act on a traveling nut to open an overhead-type garage door was shown to be conceived nearly 45 years ago by U.S. Pat. No. 2,056,174. Cable-operated or chain-operated garage door operators have also been proposed, for example, as shown by U.S. Pat. Nos. 3,439,727 and 3,444,650. Typically, garage door operators are ones which have a traverse of the door operator mechanism of about eight or nine feet in order to accommodate the usual garage door plus the 90-degree angle through which the door turns. In the chain-type of garage door operator that has been manufactured, it has been customary for many years to shorten the package in which the door operator is shipped by cutting the guide channel into two or three parts which may be spliced together. Thus, the channel which was previously nine feet long now comprises three parts of about three feet in length. However, the screw drive door operators which have been marketed for many years have retained a one-piece screw and a one-piece guide means of about nine feet in length, which makes the package costs higher and, more importantly, makes the shipping and storage costs higher because the shipping charges are usually based upon the cubic volume rather than on the weight.
Recently, there has appeared on the market a screw drive garage door operator wherein the guide means is in two parts and the screw is in two parts and interconnected by coupling means which has an interconnecting link with a pivot pin at each end pivoted to the two screw parts. The guide means and screw parts are folded for shipment and then, upon installation, are straightened to be coaxial, and splice plates are bolted onto the sides of the guide means to maintain the coaxial alignment of the screw parts. A problem with such construction is the weakness of this coupling relative to the rest of the screw, the problem of providing a properly straightened guide means, and the problem of whipping of the screw during rotation which, because of two different pivot points, acts somewhat like a universal joint to whip around inside the guide means.
More importantly, the coupling for the two screw parts has so many different parts that the possible cumulative error in the tolerance of all these manufactured parts can make it possible that the threads on the two screw parts will be mismatched relative to the traversing partial nut, and thus the nut will fail to traverse this elongated coupling. Also, the very many parts in such coupling means and the necessary clearance between the parts in order to fold means that the coupling will tend to destroy itself upon repeated reversals of the screw. In practically all screw drive garage door openers, the motor reverses each time it is started, first driving the screw clockwise and then driving it counterclockwise in order that the nut traverses forward and then in reverse for closing and opening directions of the garage door. This continual reversing of torque through the coupling and the looseness or "play" in all the parts will tend to batter the coupling apart and make the clearance of the parts even greater, which will therefore create the great possibility of mismatch of the threads in the future during life of the operator, if they are not mismatched at the time of initial assembly.